No1: Balancing 1NT I'd expect something like a semi-balanced 10-11count without a five card major.
No2: unusual, as I am not in pass-out-seat and cannot have a natural 1NT-call
No3: natural with me, but might easily be played unusual. 1NT natural is quite dangerous in this spot. And should have good stop(s) and a source of tricks. Therefore it will rarely come up and the unusual use becomes attractive.
No4: unusual
No5: unusual, as it cannot be natural with the initial pass.

2. Since you've already passed, you can't have enough for a natural NT call so it's unusual.

3. With two unlimited as yet opponents bidding, many people are using this as a sandwich 1 NT that is unusual and weaker than a double in this position. It's hard to see you coming in with a NT call when the opponents have presumably already shown about half the points in the deck.

4. Unusual for the lower two unbid suits. 1 NT here is 11-14 natural, Double followed by minimum NT is 15-18, Double followed by a jump in NT is 19-20.

The general trend over the last 6+ decades is to redefine bids such as double, 1 or 2 NT, and cuebids as picture bids, with one major goal being: disrupt the opponents auction. Example: low level doubles used to be penalty, now they are constructive and descriptive (negative, support, etc.). The whole concept of the unusual NT was to not only give partner a picture of your hand but to use up a lot of the opponents' bidding space (double doesn't use up space and gives the opponents an extra bid to describe their hands, NT forces the auction to the next level).

Therefore, all but the first example would be unusual to me, differing only in strength and number of cards in the unbid suits.

1. Natural - a normal balancing NT limited by your failure to open. Probably an 11 or really horrible 12 count (I open almost all 12 counts); maybe a phenomenal 10 in a rare case. There is no need for it to be unusual, as there is nothing to be gained by preempting the opponents (RHO has nothing).

2. Unusual - two lowest unbid.

3. Can be either natural or "sandwich" depending on agreement. I don't have a strong preference, but if it's undiscussed, then "standard" is natural.

The case for sandwich is that you won't generally have 15-18 here, and if you do, 1NT is a bit risky. Using 1NT to show 5/5 means that X shows a less shapely hand and 2NT shows 6/5 or better

The case for natural is that a lot of players respond to 1m bids on fertilizer nowadays, so the hand could well belong to your side (maybe you even have a game).

4. Natural 18+ to 20 or so.

This is important. There is no reason whatsoever to play this as unusual. There is no need to preempt; RHO has nothing. And if it's your hand, the last thing you want to do is jump the bidding with a hand of indeterminate strength.

On the other hand, there is a very good reason to play this bid as natural. Over 1D, a balancing NT is about 11-14. X followed by 1NT (if available) is 15-18 or so. 2NT immediately is 19-20. X followed by 2NT is 21-23 or so. If you don't have the jump to 2NT available, you have no way to distinguish 19 from 23. Not good.

5. Sandwich - probably 5/5 in the unbids. What else can it be if you are passed hand?

This is important. There is no reason whatsoever to play this as unusual. There is no need to preempt; RHO has nothing. And if it's your hand, the last thing you want to do is jump the bidding with a hand of indeterminate strength.

On the other hand, there is a very good reason to play this bid as natural. Over 1D, a balancing NT is about 11-14. X followed by 1NT (if available) is 15-18 or so. 2NT immediately is 19-20. X followed by 2NT is 21-23 or so. If you don't have the jump to 2NT available, you have no way to distinguish 19 from 23. Not good.

Hi Mike, I agree with the other responses. I also agree that standard is for #4 to be natural. Nethertheless I would argue that it is possible (and arguably desirable) to play a protective 2Nt as a two-suiter.

To answer your points: (1) I agree that there is little need to pre-empt in this position, but this doesn't mean that a two-suited bid can't be useful. (2) It is certainly possible to make the NT ranges work. We are not the only pairs playing a wide range 1NT protective over-call (with a Crowhurst type enqiry).

This is important. There is no reason whatsoever to play this as unusual. There is no need to preempt; RHO has nothing. And if it's your hand, the last thing you want to do is jump the bidding with a hand of indeterminate strength.

On the other hand, there is a very good reason to play this bid as natural. Over 1D, a balancing NT is about 11-14. X followed by 1NT (if available) is 15-18 or so. 2NT immediately is 19-20. X followed by 2NT is 21-23 or so. If you don't have the jump to 2NT available, you have no way to distinguish 19 from 23. Not good.

Disagree. With 2 - suiters of intermediate strength we use up bidding room while defining our own hands. With very strong hands we save space by doubling then cue bidding (or doubling again, depending upon the level of the auction). I agree that your sequence was the usual approach, and is still common, but it is not "standard expert" around here largely because of the rarity of huge NT hands in front of an opening bid..

I agree that your sequence was the usual approach, and is still common, but it is not "standard expert" around here largely because of the rarity of huge NT hands in front of an opening bid..

Perhaps people think differently over a 1♦ opener, but a BridgeWinners poll for a balancing 2nt over a 1♠ opener showed less than 10% of people voting for it showing the minors: https://bridgewinner.../balancing-2nt/

Feel free to send me a friend challenge of any format as often as you like. I'll always accept :)

Disagree. With 2 - suiters of intermediate strength we use up bidding room while defining our own hands. With very strong hands we save space by doubling then cue bidding (or doubling again, depending upon the level of the auction). I agree that your sequence was the usual approach, and is still common, but it is not "standard expert" around here largely because of the rarity of huge NT hands in front of an opening bid..

I don't know where "around here" is, but in the USA, (1D) p (p) 2NT is overwhelmingly played as a strong bid.

Hi Mike, I agree with the other responses. I also agree that standard is for #4 to be natural. Nethertheless I would argue that it is possible (and arguably desirable) to play a protective 2Nt as a two-suiter.

To answer your points: (1) I agree that there is little need to pre-empt in this position, but this doesn't mean that a two-suited bid can't be useful. (2) It is certainly possible to make the NT ranges work. We are not the only pairs playing a wide range 1NT protective over-call (with a Crowhurst type enqiry).

We do this too, but still play the protective 2NT bid as strong.

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